Device for cutting steel ropes, hawsers, chains, cables and the like under the water surface

ABSTRACT

Apparatus adapted for movement underwater to partially surround and cut underwater anchoring means such as steel ropes, hawsers, chains, cables and the like including a housing carrying an explosive cutting charge and having an arm pivotally mounted in the housing and extending therefrom. The arm is biased for movement to an open position and carries charge igniting means responsive to contact by the anchoring means to be cut in the open position of the arm for detonating the charge and severing the anchoring means. The charge igniting means is provided with several safety devices including a shear pin which is ruptured by contact with the anchoring means and a piston chamber which must be filled with water to enable detonation of the charge, thereby requiring the apparatus to be submerged. The arm may also be restrained from assuming the open position by a wire connecting the arm and the housing which is broken by contact with the anchoring means to be cut. The apparatus is adapted to be disposed of after a single use.

United States Patent [1 1 Sabranski et al.

[ DEVICE FOR CUTTING .STEEL ROPES,

HAWSERS, CHAINS, CABLES AND THE LIKE UNDER THE WATER SURFACE [75] Inventors: Udo Sabranski, Schiefbahn;

Theodor Weber; Wolfram Werner, both of Dusseldorf, all of Germany [73] Assignee: Rheinmetall GmbH, Dusseldorf,

Germany 22 Filed: Oct. 20,1971

211 App]. No.: 190,923

[30] Foreign Application Priority Data [451 Dec. 4, 1973 Primary Examiner-Milton Buchler Assistant Examiner-Gregory W. OConnor Attorney-Craig, Antonelli & Hill [57] ABSTRACT Apparatus adapted for movement underwater to partially surround and cut underwater anchoring means such as steel ropes, hawsers, chains, cables and the like including a housing carrying an explosive cutting charge and having an arm pivotally mounted in the housing and extending therefrom. The arm is biased for movement to an open position and carriescharge igniting means responsive to contact by the anchoring means to be cut in the open position of the arm for detonating the charge and severing the anchoring means. The charge igniting means is provided with several safety devices including a shear pin which is ruptured by contact with the anchoring means and a piston chamber which must be filled with water to enable detonation of the charge, thereby requiring the apparatus to be submerged. The arm may also be restrained from assuming the open position by a wire connecting the arm and the housing which is broken by contact with the anchoring means to be cut. The

apparatus is adapted to be disposed of after a single use.

30 Claims, 4 Drawing Figures DEVICE FOR CUTTING STEEL ROPESJIAWSERS,

CHAINS, CABLES AND THE LIKE UNDER WATER SURFACE This invention relates to a device forcutting steel ropes, haws'ers, chains, cables and the like under the surface of the'water; comprisinga capture and cuttings device arranged for movement towards the object to be cut to partially surround it, so that thetcuttingineans is-- actuated by theobject to be cut.-

have been used by mine SWeepingdetachmentS' for cutting anchoring devices such as steelropes, hawsers and chains to whichsea-mines, steei nets or like'devices are 1 attached; Generally, several: of "these cutting-devices are drawn through thewater on'a tow rope at aspaced distance'apart. When 'a cutting device with its capture arms arranged atan angle'to each other comes into the vicinity of a steel rope, theropeis guidedalong the capture arms into a chamber havingsa widened-portion be hind the intersectionof the arms-in which "a-chisel like.

tool is countersunkzThetool is held taut= by'a springtor is actuated by a propelli'ngcharge such'that when" the steel rope penetrates the chamber, a projecting pin is depressed for actuating the spring or awcocked firingg pin such'that the releasingof the springor the ignition of the propelling ch'arge causes the chisel to be rapidly:

forced against the steel rope;

The prior art cutting devices operatrng;-in'theabove-- described manner have generally proven'successful in all instances in which a specified-cross section=is not'ex-- ceeded by the steel ropes or chains to be cutz However; these cutting tools driven by conventionalmeans are" very large and heavy so that to achieve an-increase in efficiency, an eaven heavier embodiment would have to be used. In addition, cutting devices ofthis' type areequipped throughout 'with' their 'own' 'buoyancy mem bers. When the ropes, hawsers or chains'are not' 'cut during their first passage through the cutting; device;- then the cutting device is applied again. However, if the second pass does not result in complete cutting, then-agrappling rope is generally paid 'out from 'the mine: sweeper and is utilized for tearing the steel' rope' or chain-from its anchorage. Dueto the buoyancy'of sea-' mines, the latter can then be disarmed at'the water surface.

The present invention overcomes" the aforementioned disadvantages by ;providing a-cutting device-for I underwater steel ropes, hawsers, chains, cables *andthe like having an improved cutting efficiency and a'simple construction. The cutting device is preferably formed of such materials that the cuttingzdeviceis economi cally disposable after a single use and is 'not'dependant vi upon" additional buoyancy elements for floating through the'water.

According to the presentinventiomthere is providedbe cut.-The capture-and cutting deviceis'provided'with a cutting charge carrier, anarm' pivotable -to*an"open=' position, and means for restraining Jthe-arm" against 'as- In maritime and river navigation, cutting devices suming the open position suchthat when the device *is in the open position,= it cooperates with the object to be-:-,

cut to cause the'ignition 0f thecuttingjcharge.

In accordance with an advantageous feature of the present invention, the pivotablearm is constructed as an" angle lever havinga control plate' such that in an open position, the-arm can beoperated by, the object to be cut so that a laterally projecting retaining ring'on the-control plate brings about the release of a springloaded'piston. The working stroke ofthe piston is transmitted via a water column in the pistonchamber to a push rod'which' movesa-rockerarm mounted on a pivotablearmand carrying anignition' pin for igniting afi'ri-ng detonator associated with "the cutting charge.

In'accordance with-another feature ofthe present invention, them which is mounted-in a-recess of the cuttingcharge-carrier is provided with aspringdocated about springaxis for biasing'the' arm'into an o'penposk tion.-A'reta'ining wire which is adapted-to be destroyed by the'object'to'becut connects the cutting charge carrier and'th'earmand maintains the arm in the closed position against the opening pressure of the spring. Also,the-ignition of the'cutting charge by the firing pin is only possible'accordingto the invention after removingga-safety device.

The present' invention provides several safety devices for the cutting apparatus including a shear pin connectin g'the control plate to the pivotable arm which must Y be-ruptured before the firing pincan ignite the cutting charge. In addition, the operation of the ignition device is only possible under water in that the actuating means forthe firingpin'includes a water column with'an entry slot and asmalllatera'l outlet bore interposed between mechanical actuating means for the firing pin.

In' accordance witli still another feature of the presentfinvention, the cutting charge carrier is provided gs withastabilizer and aceramic plate is located between the cutting charge and tow rope to protect the tow rope from damage by detonation of the charge. In addition; both'thehousing of-thecutting charge carrier and the arm areconstructed essentially of plastic material to" "provide an extremely'lightweight cutting device capableof floating without additional buoyancy members.

It istherefore an'object of the present invention to provide-a devicefor cutting'underwater anchoring devices which overcomes the disadvantages of the prior art.

It is another object of the present invention to provide an inexpensive cutting device-which is disposable It isafutth'er object of the present invention to pro'-' vide'an underwater cuttingdevice requiring submersion for operation;

These-and other objects, features and advantages of thepresent invention-will become more obvious from thefollowingdescription when taken in connection with' the accompanying drawings, wherein:

device=in accordance with the present invention;

FlGs2-is a longitudinalsection through the cutting device'of FIG. 1 with the pivotable-arm in closed position;

FlG.-'3 -is' a cutaway viewof FIG.-2 with the pivotable I arm in-the open position and a firing pin readied for igniting the charge.

FIG 1 is a perspective viewof a capture and cutting- FIG. 4 is the same cutaway view. as in FIG. 3 showing a firing detonator pierced by the firing pin.

Referring now to the drawings wherein like reference numerals are used throughout the various views to designate like parts and more particularly to FIG. 1, there is shown a cutting charge carrier housing 1 preferably formed of a plastic material and receiving a cutting charge 2 having a hollow charge effect, a connecting means 4 for a tow rope 5 located at the transition point of the housing and a stabilizer 3. As shown in FIG. 2, a ceramic plate 6 is embedded in the housing between the tow rope 5 and the cutting charge 2 which is provided with a conventional metal lining to improved the charge cutting efficiency. A firing detonator 7 is in contact with the cutting charge 2 and serves initially for firing the charge.

The housing 1 is provided with an aperture 8 adjacent to the cutting charge 2 and extending to the upper edge of the housing 1 and a pivotable arm 9 preferably formed of a plastic material and having a configuration of an angle lever is arranged within the aperture for pivoting about a pivot 24. A spring 11 wound around a spring shaft biases the arm 9 into the open position. However, a retaining wire 12 connects the cutting charge carrier housing 1 and the arm 9 for preventing the arm from assuming the open position. The retaining wire 12 is adapted to be destroyed by the object 27 to be cut, or the wire may be removed by hand. In the closed position, i.e., in the unaffected condition of the wire 12, the cutting charge carrier 1 and the arm 9 are both provided with guiding surface configurations which aid the capture of the object to be cut.

As shown in FIG. 2, when the arm 9 is in the closed position, the short end of the angle lever forming the arm is disposed in the aperture 8 and a control plate 13 secured in the arm by a shear pin 9a is disposed deep in the cavity of the cutting charge 2. The control plate includes a projecting retaining ring 15 and the plate is pivoted on the arm 9 by a pivot 14. The shear pin serves as a safety device for preventing improper charge detonation by preventing pivoting of the control plate until sufficient pressure is exerted on the control plate to rupture the pin.

A collar 16 of a piston 17 is biased into abutment against the retaining ring 15 by a compression spring 18 which actuates the piston with the portion of the piston above the collar 16 being guided in a piston chamber 19. Above the piston 17, the piston chamber is provided with a lateral slot 20 as an inlet and a small lateral bore 21 as an outlet. In the continuation of the piston chamber 19, a push-rod 22 is movably mounted in the arm 9 for striking the side edge of a rocker arm 23 mounted on the pivot 24. A leaf spring 26 supported on the rocker arm 23 and the inner wall of the arm 9 constantly biases the rocker arm 23 against the push rod 22 and an ignition pin 25 projects downwardly from the opposite end of the rocker arm 23.

In operation as an underwater cutting device, a plurality of the cutting devices are connected to the tow rope of a mine sweeper at a predetermined spacing. The free end of the two rope 5 is provided with a float having fins which permits the tow rope 5 to be held in a wide are out of the wash of the ship, thus enabling the tow rope to cover an area as wide as possible; In accordance with the present invention, the formation of the housing and arm from plastic material provides extraordinarily light cutting devices with flat stabilizers 3 which require noadditional buoyancy members. As the cutting device submerges, the water penetrates the piston chamber 19 throughthe slot 20 and forms a water column 28 to complete the firing pin actuating mechanism. A small amount of water'leaves the piston chamber 19 through the small lateral bore 21. However, the chamber is constantly refilled through the slot 20.

As the cutting device is carried through the water, an object 27 to be cut, e.g., a steel rope, arrives in front of the retaining wire 12 breaking the wire so that the force of the spring 11 causes the entire arm 9 to be brought into the open position as shown in FIG. 3. It is, of course, also possible to remove the retaining wire 12 by hand, before inserting the cutting device in the water, so that the arm 9 is in the open position. This solution has the advantage that the open capture device covers a greater area and has a greater chance of catching a steel rope than a closed device. In the open position, the point of the ignition pin 25 is located immediately in front of the firing detonator 7 of the cutting charge 2. As the steel rope 27 is surrounded by the capture device, the rope presses against the control plate 13 causing the safety shear pin to rupture. This results in the retaining ring 15 being displaced in such a way that the collar 16 of the piston 17 is released and forced forward by the compression spring 18 to strike the water column 28. The pressure of the water column 28 operates on the push-rod 22 forcing the push-rod from its seat to actuate the rocker arm 23 against the force of the leaf spring 26 and causing the rocker arm to pivot about pivot 24 so that the point of the ignition pin 25 punctures the firing detonator 7. The firing detonator ignites the cutting charge 2 and since the steel rope 27 to be cut is exactly in front of the cutting charge 2, it is broken cleanly by the cutting blast of the detonating cutting charge.

The cutting charge, upon ignition by the detonator 7 deforms the metallic lining into a cutting edge, which cuts through the steel rope or an anchoring hawser, a chain or even a cable at high speed. However, it is desired that the tow rope 5 should not be unduly damaged by the charge. For this purpose, the ceramic plate 6 is arranged as a protective screen between the cutting charge 2 and the tow rope 5 to prevent damage of the tow rope. After combing an area of sea-mines, the burnt-out cutting devices are removed from the tow rope, thrown away and replaced by new ones, so that during the next passage the adjacent area can be combed.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It should therefore be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

We claim:

1. Apparatus adapted for movement underwater to partially surround and cut an underwater anchoring means such as a steel rope or chain comprising a housing, cutting charge carried by said housing, arm means connected to said housing and mounted for pivotable movement into an open position with respect to said housing, said arm means in the open position being responsive to the anchoring means for igniting said cutting charge to sever the anchoring means, and means for restraining the movement of said arm means into the open position.

means includes means carried thereby and arranged for contacting the anchoring means in the open position of said arm means and responsive thereto for igniting said cuttingcharge.

3. Apparatus as defined in claim 1 wherein said restraining means is a wire connecting said housing and said arm means, said wire adapted to be broken by contact with the anchoring means thereby permitting said arm means to assume the open position.

4. Apparatus as defined in claim 1 wherein said housing is provided with an aperture, said arm means being pivotably mounted in said aperture, and a spring is arranged in said aperture for biasing said arm means into the open position.

.5. Apparatus as defined in claim 4 wherein said arm means is formed as an angle lever and includes means carried thereby and arranged for contacting theanchoring means in the, open position, of said; am. means. and responsive thereto. for igniting said. cutting; charge.

6. Apparatus asdefined in claim 5, wherein said. igniting means includes a control plate mountedfor pivotal; movement in response to contact bythe anchoring means, a rocker arm. mounted for pivotal movement and carrying an igniting pin for contactingsaid cutting charge to ignite said charge, and actuating means-responsive to the pivotal movement of saidcontrol plate for causing movement of saidrockerarmandzsaid ignifi ing pin whereby said igniting pin ignites. said. cutting to the movement of said pison-via, the water: in said chamber for pivoting said rocker arm to.c,ause. ignition;

of said charge by said igniting pin.

8. Apparatus as defined in claim 7 wherein-saidicon-v trol :plate includes a retaining ring extending therefromin abutment with a portion of said piston-to prevent movement of piston in response to the springforcewhereby movement of said control plate-causes the. re-

taining ring to move out of abutmentwith saidipiston to permit movement of said piston in response to the. spring force.

9. Apparatus as defined in claim 8.wherein said con-. trol plate is provided with means fixedly connecting said control plate to said arm means, said means-being ruptured in response to said control plate.,-contacting the anchoring means to permit-pivotal movemenLof said control plate.

10 Apparatus as defined in claim 9 wherein said con-v necting means is a shearpin.

11.- Apparatus as defined in claim 7 wherein said piston chamber is provided with alateral inlet-slot and a.

small lateral outlet .bore for permitting ;water.to enter and fill said chamber when saidapparatus is-xsub merged.

12; Apparatus as defined in claim 8- wherein said cutting charge is provided with, a firing-detonator and said igniting pin contactssaid firing detonatonsfor-igniting, said cutting charge.

13. Apparatus as defined in. claimpl .wherein said housing is provided withza stabilizer- 14. Apparatus as defined in claimJ-Fwhereinsaid housing includes means for connectinga tow rope for:

towing said apparatus through the water and a ceramic plate is disposed in said housing between said cutting charge and-said tow rope connecting means for shielding the tow rope from the charge detonation.

15. Apparatus as defined :in claim 14, wherein said charge is provided with ametal lining and said ceramic plate is arranged substantially parallel to said charge and said tow rope connecting means.

17. Apparatus as defined in claim 8 wherein saidpushrod is arranged at one end of said piston chamber adapted; for contact with: the water in said chamber and .a spring is provided in said arm means for biasing said rocker arm into contact with said push-rod whereby the force of the movement of said piston is transmitted to said; push rod= via the water in said chamber causing the push-rod: to pivot said rocker arm against the bias of i said spring.

l=8. Apparatus asdefined in claim 17 wherein said housing isprovid'edwith arecess inwhich said 'cutting.

charge is carried; said control plate being positioned along-said. arm means proximate to said recess.

19; Apparatus as defined in claim 18 wherein said controlplate is receivedin saidrecess in the closed position of said armmeans.

20..Apparatus as defined in claim 8 wherein a wire connectssaidhousingandsaid-arm means for restraining-the movementof said'arm meansinto the open position, said wire adapted-tobe broken by contact with the anchoring means thereby permitting said arm means to assume the open I position.

21'. Apparatus as definedin claim 20'wherein said housingisprovidedwith astabilizer portion extending therefromiand acerarnic plate is disposed in said housing between-saidacuttingmharge and said stabilizer portion.

22;,Apparatus -as defined in claim 21 wherein said arm'means and:said housing is formed of plastic material. 1

23.-Apparatus as defined in claim 2 wherein said ig niting means includes a control plate mounted for pivotal movementiin response to contact by the anchoring means, a-rocken arm mounted for pivotal'movement and carrying'an igniting pin for contacting said cutting charge toignite saidcharge, and actuating means re-' sponsiveto the pivotal movement *of said control plate forcausing movement of said rocker arm and said ignit-' ingpimwh'ereby said'igniting pin ignites said cutting charge.

24: Apparatus as defined in claim 23 wherein said actuating means includes a piston chamber adapted to be filled :with water, as ring'biased piston arranged for movement-zinsaid chamber in response to the movementof'saidcontrol plate, and a push-rod responsive to :the movementof said piston via the water in said chamber -for.pivoting. said rocker arm to cause ignition ofisaid charge by said igniting pin:

25-. Apparatus as defined in claim 3 wherein said arm means includes means carried thereby and arranged for contacting-the anchoring-means inthe open position of said. arm'means and responsive thereto for igniting said cutting charge.

26t Apparatus as defined in claim 25 wherein said igniting-means includes acontrol plate mounted for piv= otal movement in=response to contact by the anchoring means, a rocker arm mounted for pivotal movement and carrying an igniting pin for contacting said cutting charge to ignite said charge, and actuating means responsive to the pivotal movement of said control plate for causing movement of said rocker arm and said igniting pin whereby saidigniting pin ignites said cutting charge.

27. Apparatus as defined in claim 26 wherein said actuating means includes a piston chamber adapted to be filled with water, a spring biased piston arranged for movement in said chamber in response to the movement of said control plate, and a push-rod responsive to the movement of said piston via the water in said chamber for pivoting said rocker arm to cause ignition of said charge by said igniting pin.

28. Apparatus as defined in claim 16 wherein said arm means includes means carried thereby and arranged for contacting the anchoring means in the open position of said arm means and responsive thereto for igniting said cutting charge.

29. Apparatus as defined in claim 28 wherein said igniting means includes a control plate mounted for pivotal movement in response to contact by the anchoring means, a rocker arm mounted for pivotal movement and carrying an igniting pin for contacting said cutting charge to ignite said charge, and actuating means re sponsive to the pivotal movement of said control plate for causing movement of said rocker arm and said igniting pin whereby said igniting pin ignites said cutting charge.

30. Apparatus as defined in claim 29 wherein said actuating means includes a piston chamber adapted to be filled with water, a spring biased piston arranged for movement in said chamber in response to the movement of said control plate, and a push-rod responsive to the movement of said piston via the water in said chamber for pivoting said rocker arm to cause ignition of said charge by said igniting pin. 

1. Apparatus adapted for movement underwater to partially surround and cut an underwater anchoring means such as a steel rope or chain comprising a housing, cutting charge carried by said housing, arm means connected to said housing and mounted for pivotable movement into an open position with respect to said housing, said arm means in the open position being responsive to the anchoring means for igniting said cutting charge to sever the anchoring means, and means for restraining the movement of said arm means into the open position.
 2. Apparatus as defined in claim 1 wherein said arm means includes means carried thereby and arranged for contacting the anchoring means in the open position of said arm means and responsive thereto for igniting said cutting charge.
 3. Apparatus as defined in claim 1 wherein said restraining means is a wire connecting said housing and said arm means, said wire adapted to be broken by contact with the anchoring means thereby permitting said arm means to assume the open position.
 4. Apparatus as defined in claim 1 wherein said housing is provided with an aperture, said arm means being pivotably mounted in said aPerture, and a spring is arranged in said aperture for biasing said arm means into the open position.
 5. Apparatus as defined in claim 4 wherein said arm means is formed as an angle lever and includes means carried thereby and arranged for contacting the anchoring means in the open position of said arm means and responsive thereto for igniting said cutting charge.
 6. Apparatus as defined in claim 5 wherein said igniting means includes a control plate mounted for pivotal movement in response to contact by the anchoring means, a rocker arm mounted for pivotal movement and carrying an igniting pin for contacting said cutting charge to ignite said charge, and actuating means responsive to the pivotal movement of said control plate for causing movement of said rocker arm and said igniting pin whereby said igniting pin ignites said cutting charge.
 7. Apparatus as defined in claim 6 wherein said actuating means includes a piston chamber adapted to be filled with water, a spring biased piston arranged for movement in said chamber in response to the movement of said control plate, and a push-rod responsive to the movement of said pison via the water in said chamber for pivoting said rocker arm to cause ignition of said charge by said igniting pin.
 8. Apparatus as defined in claim 7 wherein said control plate includes a retaining ring extending therefrom in abutment with a portion of said piston to prevent movement of piston in response to the spring force whereby movement of said control plate causes the retaining ring to move out of abutment with said piston to permit movement of said piston in response to the spring force.
 9. Apparatus as defined in claim 8 wherein said control plate is provided with means fixedly connecting said control plate to said arm means, said means being ruptured in response to said control plate contacting the anchoring means to permit pivotal movement of said control plate.
 10. Apparatus as defined in claim 9 wherein said connecting means is a shear pin.
 11. Apparatus as defined in claim 7 wherein said piston chamber is provided with a lateral inlet slot and a small lateral outlet bore for permitting water to enter and fill said chamber when said apparatus is submerged.
 12. Apparatus as defined in claim 8 wherein said cutting charge is provided with a firing detonator and said igniting pin contacts said firing detonator for igniting said cutting charge.
 13. Apparatus as defined in claim 1 wherein said housing is provided with a stabilizer.
 14. Apparatus as defined in claim 1 wherein said housing includes means for connecting a tow rope for towing said apparatus through the water and a ceramic plate is disposed in said housing between said cutting charge and said tow rope connecting means for shielding the tow rope from the charge detonation.
 15. Apparatus as defined in claim 14, wherein said charge is provided with a metal lining and said ceramic plate is arranged substantially parallel to said charge and said tow rope connecting means.
 16. Apparatus as defined in claim 1 wherein said housing and said arm means are formed of plastic material.
 17. Apparatus as defined in claim 8 wherein said push-rod is arranged at one end of said piston chamber adapted for contact with the water in said chamber and a spring is provided in said arm means for biasing said rocker arm into contact with said push-rod whereby the force of the movement of said piston is transmitted to said push rod via the water in said chamber causing the push-rod to pivot said rocker arm against the bias of said spring.
 18. Apparatus as defined in claim 17 wherein said housing is provided with a recess in which said cutting charge is carried, said control plate being positioned along said arm means proximate to said recess.
 19. Apparatus as defined in claim 18 wherein said control plate is received in said recess in the closed position of said arm means.
 20. Apparatus as defined in claim 8 wherein a wire connects said housing and said arm means fOr restraining the movement of said arm means into the open position, said wire adapted to be broken by contact with the anchoring means thereby permitting said arm means to assume the open position.
 21. Apparatus as defined in claim 20 wherein said housing is provided with a stabilizer portion extending therefrom and a ceramic plate is disposed in said housing between said cutting charge and said stabilizer portion.
 22. Apparatus as defined in claim 21 wherein said arm means and said housing is formed of plastic material.
 23. Apparatus as defined in claim 2 wherein said igniting means includes a control plate mounted for pivotal movement in response to contact by the anchoring means, a rocker arm mounted for pivotal movement and carrying an igniting pin for contacting said cutting charge to ignite said charge, and actuating means responsive to the pivotal movement of said control plate for causing movement of said rocker arm and said igniting pin whereby said igniting pin ignites said cutting charge.
 24. Apparatus as defined in claim 23 wherein said actuating means includes a piston chamber adapted to be filled with water, a spring biased piston arranged for movement in said chamber in response to the movement of said control plate, and a push-rod responsive to the movement of said piston via the water in said chamber for pivoting said rocker arm to cause ignition of said charge by said igniting pin.
 25. Apparatus as defined in claim 3 wherein said arm means includes means carried thereby and arranged for contacting the anchoring means in the open position of said arm means and responsive thereto for igniting said cutting charge.
 26. Apparatus as defined in claim 25 wherein said igniting means includes a control plate mounted for pivotal movement in response to contact by the anchoring means, a rocker arm mounted for pivotal movement and carrying an igniting pin for contacting said cutting charge to ignite said charge, and actuating means responsive to the pivotal movement of said control plate for causing movement of said rocker arm and said igniting pin whereby said igniting pin ignites said cutting charge.
 27. Apparatus as defined in claim 26 wherein said actuating means includes a piston chamber adapted to be filled with water, a spring biased piston arranged for movement in said chamber in response to the movement of said control plate, and a push-rod responsive to the movement of said piston via the water in said chamber for pivoting said rocker arm to cause ignition of said charge by said igniting pin.
 28. Apparatus as defined in claim 16 wherein said arm means includes means carried thereby and arranged for contacting the anchoring means in the open position of said arm means and responsive thereto for igniting said cutting charge.
 29. Apparatus as defined in claim 28 wherein said igniting means includes a control plate mounted for pivotal movement in response to contact by the anchoring means, a rocker arm mounted for pivotal movement and carrying an igniting pin for contacting said cutting charge to ignite said charge, and actuating means responsive to the pivotal movement of said control plate for causing movement of said rocker arm and said igniting pin whereby said igniting pin ignites said cutting charge.
 30. Apparatus as defined in claim 29 wherein said actuating means includes a piston chamber adapted to be filled with water, a spring biased piston arranged for movement in said chamber in response to the movement of said control plate, and a push-rod responsive to the movement of said piston via the water in said chamber for pivoting said rocker arm to cause ignition of said charge by said igniting pin. 